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Message-ID: <42140EFD.2020104@austin.rr.com>
Date: Wed, 16 Feb 2005 21:26:53 -0600
From: Dennis Haverlah <clouduster@austin.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Vapor Lock
References: <list-741488@logan.com>
In-Reply-To: <list-741488@logan.com>
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Without a Facet pump between the tank and the HP and you have a vapor 
lock at the HP pump you will have no flow.  With the Facet at the tank 
it will prime the HP pump by pushing  liquid fuel into the HP pump.  
Once the vapor lock is gone, the HP can suck through the Facet even when 
it is running.  How much flow is really coming out of an HP pump with a 
normal FI system with a return to the tank.  I doubt is it 30 + gph.  I 
guess I's saying the HP pump will be operating at much less than its 
max. rated capacity and the system with the Facet between the tank and 
the HP pump should work fine.  I'm considering this system for my RV 7A.

Dennis H.

Jim Sower wrote:

> <... HP pumps are capable of moving LOTS more fuel than a Facet pump 
> ... HP pumps would be drawing fuel through the Facet pump ... because 
> the Facet can't keep up ...>
>
> You're right.  I hadn't thought of that.  Facet pumps deliver 30 gph.  
> I'll check how much my HP pumps are putting out.  Wonder if Facet 
> delivers more at lower head pressure, objective being to push fuel 
> through filter and plumbing so there's less chance of pressure drop 
> that could cause the fuel to vaporize.
>
> Back to the drawing board ... maybe ... Jim S.
>
> Marvin Kaye wrote:
>
>> Jim Sower <canarder@frontiernet.net> wrote:
>>
>> """
>>  I have a canard, but I will have a Facet pump near (and below) the 
>> wing tanks
>> to PUSH the fuel through the filter and fuel flow transducer.  I 
>> don't want
>> the HP pumps to SUCK through the filters and etc. for fear of 
>> vaporizing the
>> fuel.
>> """
>>
>> This doesn't make any sense to me, but perhaps I'm missing 
>> something.  The HP pumps are capable of moving LOTS more fuel than a 
>> Facet pump.  Consequently, it seems to me that the HP pumps would 
>> actually be drawing fuel through the Facet pump when they're switched 
>> on, simply because the Facet can't keep up with what's being drawn 
>> out of the sump tank by them.  Additionally, a return system needs 2 
>> flow transducers, one for the feed line and one for the return... 
>> then the display instrument's electronics deduct the return flow from 
>> the feed flow to properly calculate actual through-the-injectors 
>> instantaneous flow data.  (The EI fuel flow instrument uses an FFDM-1 
>> (fuel flow differential module) to do the job, GRT EIS does it 
>> itself, as do other flow instruments with both feed and return inputs.)
>>
>> As long as the filters are rated to flow as much fuel as the HP pumps 
>> are capable of pushing I don't see that (vapoization) as an issue.  
>> The filter elements do need to be kept clean, and are a 
>> replace-at-annual item.
>>
>>    <Marv>
>>
>>>>  Homepage:  http://www.flyrotary.com/
>>>>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>>>
>>>
>>
>>
>
>>>  Homepage:  http://www.flyrotary.com/
>>>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>>
>

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Without a Facet pump between the tank and the HP <u>and you have a
vapor lock at the HP pump you will have no flow</u>.&nbsp; With the Facet at
the tank it will prime the HP pump by pushing&nbsp; liquid fuel into the HP
pump.&nbsp; Once the vapor lock is gone, the HP can suck through the Facet
even when it is running.&nbsp; How much flow is really coming out of an HP
pump with a normal FI system with a return to the tank.&nbsp; I doubt is it
30 + gph.&nbsp; I guess I's saying the HP pump will be operating at much
less than its max. rated capacity and the system with the Facet between
the tank and the HP pump should work fine.&nbsp; I'm considering this system
for my RV 7A.<br>
<br>
Dennis H.<br>
<br>
Jim Sower wrote:
<blockquote cite="midlist-741488@logan.com" type="cite">&lt;... HP
pumps are capable of moving LOTS more fuel than a Facet pump ... HP
pumps would be drawing fuel through the Facet pump ... because the
Facet can't keep up ...&gt;
  <br>
  <br>
You're right.&nbsp; I hadn't thought of that.&nbsp; Facet pumps deliver 30 gph.&nbsp;
I'll check how much my HP pumps are putting out.&nbsp; Wonder if Facet
delivers more at lower head pressure, objective being to push fuel
through filter and plumbing so there's less chance of pressure drop
that could cause the fuel to vaporize.
  <br>
  <br>
Back to the drawing board ... maybe ... Jim S.
  <br>
  <br>
Marvin Kaye wrote:
  <br>
  <br>
  <blockquote type="cite">Jim Sower <a class="moz-txt-link-rfc2396E" href="mailto:canarder@frontiernet.net">&lt;canarder@frontiernet.net&gt;</a>
wrote:
    <br>
    <br>
"""
    <br>
&nbsp;I have a canard, but I will have a Facet pump near (and below) the
wing tanks
    <br>
to PUSH the fuel through the filter and fuel flow transducer.&nbsp; I don't
want
    <br>
the HP pumps to SUCK through the filters and etc. for fear of
vaporizing the
    <br>
fuel.
    <br>
"""
    <br>
    <br>
This doesn't make any sense to me, but perhaps I'm missing something.&nbsp;
The HP pumps are capable of moving LOTS more fuel than a Facet pump.&nbsp;
Consequently, it seems to me that the HP pumps would actually be
drawing fuel through the Facet pump when they're switched on, simply
because the Facet can't keep up with what's being drawn out of the sump
tank by them.&nbsp; Additionally, a return system needs 2 flow transducers,
one for the feed line and one for the return... then the display
instrument's electronics deduct the return flow from the feed flow to
properly calculate actual through-the-injectors instantaneous flow
data.&nbsp; (The EI fuel flow instrument uses an FFDM-1 (fuel flow
differential module) to do the job, GRT EIS does it itself, as do other
flow instruments with both feed and return inputs.)
    <br>
    <br>
As long as the filters are rated to flow as much fuel as the HP pumps
are capable of pushing I don't see that (vapoization) as an issue.&nbsp; The
filter elements do need to be kept clean, and are a replace-at-annual
item.
    <br>
    <br>
&nbsp;&nbsp; &lt;Marv&gt;
    <br>
    <br>
    <blockquote type="cite">
      <blockquote type="cite">&nbsp;Homepage:&nbsp; <a class="moz-txt-link-freetext" href="http://www.flyrotary.com/">http://www.flyrotary.com/</a>
        <br>
&nbsp;Archive:&nbsp;&nbsp; <a class="moz-txt-link-freetext" href="http://lancaironline.net/lists/flyrotary/List.html">http://lancaironline.net/lists/flyrotary/List.html</a>
        <br>
      </blockquote>
      <br>
    </blockquote>
    <br>
    <br>
  </blockquote>
  <br>
  <blockquote type="cite">
    <blockquote type="cite">&nbsp;Homepage:&nbsp; <a class="moz-txt-link-freetext" href="http://www.flyrotary.com/">http://www.flyrotary.com/</a>
      <br>
&nbsp;Archive:&nbsp;&nbsp; <a class="moz-txt-link-freetext" href="http://lancaironline.net/lists/flyrotary/List.html">http://lancaironline.net/lists/flyrotary/List.html</a>
      <br>
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